Conjugated linoleic acid in milk fat: High variation depending on production system

During one year's period bulk milk samples were collected monthly from three different types of farms: 1. conventional farming-indoor feeding with silages the whole year, 2. conventional farming-grazing during summer season, 3. ecological farming-grazing during summer season. Conjugated linoleic acids (CLA), trans vaccenic and other trans isomers of milk fatty acids were analyzed. Variation of CLA in milk fat was substantial (0.26 to 1.14 % of total methyl esters) and was season-dependent. The lowest percentage of CLA (0.34 %) was found in the group, fed only fermented roughage and concentrates (most intensive production farm) the highest (0.80 %) in the ecologically produced milk fat. The concentration of CLA and trans vaccenic acid was positively correlated. There is a growing interest in CLA, considered to be beneficial in prevention of carcinogenesis. Its percentage in milk products can be increased through a suitable dietary regimen. (C) 1997 Elsevier Science Inc.